Electronic Telegram No. 5283 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network COMET P/2023 H6 = P/2010 TO_20 (LINEAR-GRAUER) M. Rudenko, Minor Planet Center, has published (cf. MPEC 2023-O88) the recovery by M. Micheli and C. Schambeau of comet P/2010 TO_20 (cf. IAUC 9235) in CCD images taken with the 8.1-m "Gemini South" telescope at Cerro Pachon, Chile, on Apr. 20 and May 25 UT. The object is presumed to have appeared stellar on all images. The astrometry by Micheli is tabulated below. 2023 UT R.A. (2000) Decl. Mag. Observer Apr. 20.39241 22 15 31.81 -13 13 43.7 23.0 Schambeau 20.39416 22 15 31.87 -13 13 43.4 23.1 " 20.39591 22 15 31.95 -13 13 42.9 " 20.39766 22 15 32.00 -13 13 42.8 23.2 " 20.39941 22 15 32.06 -13 13 42.5 23.6 " 20.40118 22 15 32.13 -13 13 42.0 22.9 " 20.40293 22 15 32.19 -13 13 41.8 " 20.40468 22 15 32.25 -13 13 41.5 23.2 " May 25.32041 22 32 24.30 -11 49 44.2 22.8 " 25.32567 22 32 24.41 -11 49 43.8 22.7 " 25.33093 22 32 24.51 -11 49 43.3 23.3 " The residuals for the above recovery observations are +4'.0 in R.A. and +1'.6 in Decl. from the prediction in NK 2433 (and the ICQ's 2020 Comet Handbook), with an indicated correction to that prediction of Delta(T) = -1.01 days. The following linked orbital elements are from 85 observations spanning 2009-2023 (mean residual 0".4). The comet passed 0.24 AU from Saturn in 1960 August, 0.35 AU from Jupiter on 2003 Aug. 26, and 0.075 AU from Jupiter on 2009 Oct. 22 UT. Those last two close approaches greatly changed the comet's orbit (as seen from the 1979 elements below. The formal error on the orbital period is now +/- 0.02 day. Note that the arc of observation was extended back more than a year by S. Deen, who reported CCD observations in publicly accessible archival image files from the 1.2-m Oschin Schmidt telescope at Palomar, dating back to three nights July 2009 (cf. MPEC 2023-B57). Epoch = 1979 Feb. 16.0 TT T = 1979 Feb. 12.02630 TT Peri. = 191.21442 e = 0.3294477 Node = 320.97466 2000.0 q = 5.8448543 AU Incl. = 1.81406 a = 8.7164777 AU n = 0.03829945 P = 25.73 years Epoch = 2004 Dec. 21.0 TT T = 2005 Jan. 9.40661 TT Peri. = 353.26123 e = 0.1020765 Node = 200.49282 2000.0 q = 5.4069546 AU Incl. = 1.20286 a = 6.0216207 AU n = 0.06670125 P = 14.78 years Epoch = 2022 Dec. 7.0 TT T = 2022 Nov. 27.07024 TT Peri. = 267.46333 e = 0.0556555 Node = 43.28223 2000.0 q = 5.5080382 AU Incl. = 2.47874 a = 5.8326579 AU n = 0.06996878 P = 14.09 years Epoch = 2036 Dec. 13.0 TT T = 2036 Nov. 24.77874 TT Peri. = 267.71539 e = 0.0548186 Node = 43.20154 2000.0 q = 5.4608757 AU Incl. = 2.48166 a = 5.7775953 AU n = 0.07097140 P = 13.89 years Epoch = 2050 Aug. 22.0 TT T = 2050 Aug. 18.89992 TT Peri. = 265.24541 e = 0.0553873 Node = 43.01712 2000.0 q = 5.4312494 AU Incl. = 2.47988 a = 5.7497102 AU n = 0.07148833 P = 13.79 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.0 and 2.5n = 7.5 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 06 25 22 37.76 -11 31.4 4.995 5.520 116.2 9.5 20.1 2023 07 05 22 37.29 -11 38.3 4.864 5.521 125.8 8.6 20.0 2023 07 15 22 35.73 -11 51.1 4.748 5.522 135.8 7.4 19.9 2023 07 25 22 33.14 -12 09.3 4.652 5.523 146.0 5.9 19.9 2023 08 04 22 29.68 -12 31.6 4.580 5.525 156.4 4.2 19.9 2023 08 14 22 25.55 -12 56.5 4.534 5.526 166.9 2.4 19.9 2023 08 24 22 21.01 -13 22.3 4.518 5.527 176.5 0.6 19.8 2023 09 03 22 16.38 -13 46.9 4.531 5.529 170.6 1.7 19.9 2023 09 13 22 11.98 -14 08.8 4.573 5.530 160.1 3.6 19.9 2023 09 23 22 08.12 -14 26.4 4.644 5.532 149.4 5.3 19.9 2023 10 03 22 05.06 -14 38.6 4.740 5.533 138.9 6.8 20.0 2023 10 13 22 02.99 -14 44.7 4.858 5.535 128.5 8.1 20.0 2023 10 23 22 02.04 -14 44.4 4.994 5.537 118.4 9.1 20.1 2023 11 02 22 02.25 -14 37.7 5.143 5.538 108.5 9.8 20.1 2023 11 12 22 03.63 -14 24.7 5.300 5.540 98.9 10.2 20.2 2023 11 22 22 06.12 -14 05.9 5.462 5.542 89.5 10.3 20.3 2023 12 02 22 09.65 -13 41.6 5.624 5.544 80.3 10.1 20.3 2023 12 12 22 14.10 -13 12.2 5.781 5.546 71.4 9.7 20.4 2023 12 22 22 19.37 -12 38.3 5.931 5.548 62.6 9.1 20.4 2024 01 01 22 25.34 -12 00.4 6.070 5.550 54.0 8.2 20.5 2024 01 11 22 31.90 -11 18.9 6.196 5.552 45.6 7.3 20.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 July 27 (CBET 5283) Daniel W. E. Green